Boasting a huge network of nerve cells, your gut literally has a mind of its own — which has a huge impact on the way you think and feel. Ravinder Lilly tells how to tap into tummy power.
Did you know you have two brains? Besides the smarts in your head, you have a network of 100 million neurons (nerve cells) stretching from your oesophagus to your colon — that’s more than you’ll find in your entire spinal cord! These neural connections form your enteric brain. The word enteric means ‘relating to the intestines’, so you could call this second brain your gut brain.
Your brains in conversation
Your two brains are in constant communication by way of the vagus nerve. (The word vagus is Latin for ‘wandering’.) This large meandering nerve starts at the back of the skull and ends in the abdomen, connecting with the ears, voice box, heart, lungs and stomach along the way. Nerve cells send and receive messages via proteins, which are chemical compounds that can alter these signals, causing both positive and negative effects.
You know the ‘butterflies’ that tickle your stomach when you’re a little anxious? Does your gut play up when you’re stressed? That means you’ve felt your gut brain communicating with the brain in your head, because this exchange is part of your body’s natural stress response.
Both your brains are affected by emotions as well as by your lifestyle choices, especially your diet. Drinks such as alcohol, soft drinks and even water have an impact on the neurons’ release of either feel-good chemicals or stress chemicals, or a mixture of both. In the case of alcohol, having one drink may help you feel relaxed, but downing one too many triggers the release of stress hormones — the opposite (and unwelcome) effect.
The trillions of bacteria living in your gastrointestinal tract also produce and release feel-good chemicals and stress chemicals. Research shows that when these probiotic microorganisms are manipulated (whether that’s by prebiotics, probiotics, antibiotics or dietary changes), our mood and behaviour can change, too. (The literal meaning of the word probiotic is ‘for life’.) Because of such findings, future psychiatric and psychological treatments may well involve both brains. At this point, you might want to remember Hippocrates’ advice to “let food be thy medicine”.
The hidden power of your gut bacteria
Your gut brain uses more than 30 types of neurotransmitters, and researchers are finding that gut microbes are in the process of producing new mind-altering neurochemicals all the time.
In the future, scientists might be able to harness these clever chemicals to create medicines that mimic the positive benefits of probiotics. Another possible scenario is that new treatments may involve identifying, growing and harvesting the microbes that make mood-boosting chemicals, enabling scientists to formulate new probiotic supplements.
In the meantime, keeping your gut microbes happily well fed is a great way to help boost your mood and your health.
Meet your friendly tenants, your body’s healthy bacteria
About 90 per cent of your body’s cells are bacterial, not human, and we’re just starting to understand their power. Scientists have been unable to observe our bacteria in the lab because microbes need a living human to survive, but here’s what we do know:
As babies in the womb, our bodies are sterile; we get our first dose of ‘good’ bacteria while passing through the birth canal
These beneficial bacteria make essential nutrients, including B-group vitamins (for energy) and vitamin K (for blood clotting and strong bones)
They also destroy potential carcinogens
Healthy bacteria may lift your mood and combat the blues
They may also help control appetite
The foods we eat play an important role in keeping our gut bacteria both healthy and diverse, and the more complex our bacterial mix, the better
So look after your gut bacteria — they’re looking after you!
Your bacterial army in battle
If the gut’s delicate balance of beneficial probiotic microbes is upset and harmful microbes (pathogens) take over, so does disease. Unfortunately, these pathogens release toxins that can depress mood. You could say that your gut bacteria are waging a constant war, as the ‘good’ probiotics battle to keep the ‘bad’ bugs at bay. To help the good guys win, try adopting the following healthy habits.
Give processed foods the push
Fatty fast food is low in fibre and plant foods, both of which provide your ‘good’ gut bacteria with the nutrients they need. Consequently, a diet full of fast food provides less food for beneficial microbes, helping potentially harmful pathogens to dominate.
Your individual mix of gut flora can even affect your appetite. The bacterium Helicobacter pylori, for example, inhibits the hunger-enhancing hormone ghrelin, thus curbing cravings. (Although H. pylori was once abundant in the digestive tract, it’s now not so prevalent.)
Gut bacteria can also influence sugar cravings. When two groups of mice consumed a sugar solution in a 2012 French study, those with healthy gut flora ate less than mice with less gut flora.
Scientists are now exploring how to manipulate the gut microbes of people who love sugar, because this could help suppress cravings for sweet foods.
Enjoy some culture
Prebiotics are carbohydrates, such as starches and fibres, that we can’t digest. As a result, prebiotics remain intact in the gut, where they become essential fuel for our healthy bacteria. Eat bananas, onions, al dente pasta and cold (cooked) potato, all of which are high in resistant starches and therefore prebiotics.
Another way to help plant more healthy flora in your gut (and crowd out potential pathogens) is to take a probiotic supplement. Having plenty of these beneficial microbes can also help your gut produce more of the proteins that have the ability to suppress appetite and increase feelings of fullness.
Probiotics have yet another welcome power — they can lower your stomach levels of substance P, a neurotransmitter that’s involved in pain, inflammation, and even anxiety and depression.
In a 2013 US study, scientists gave healthy women probiotic yoghurt. At the end of the four-week tudy, brain scans showed that the regions involved in anxiety and depression were less reactive.
Clearly, we’d all benefit from adding more probiotic foods to our diets. Yoghurts are a good natural source, so look for brands with added live cultures, such as Lactobacillus acidophilus and Bifidobacterium bifidum.
Like dill pickles and other pickled vegetables, fermented cabbage is also full of live cultures, along with vitamins A, B and E. Try traditional German sauerkraut or the spicy Korean version, kimchi. Other probiotic Asian foods include tempeh, a fermented soybean protein that can take the place of meat in your meals, and miso, a paste made from fermented rye, beans, rice or barley. Add a tablespoon of miso to warm water for a quick soup with a probiotic blast!
Staying active supports the function of your gastrointestinal tract, helping it expel waste from your system. Physical activity may even benefit gut microbes, according to a small 2014 Irish study of elite rugby players. Although the athletes in this study trained much harder than the average person, they also ate more food, including plenty of fruit and vegies. As a result, they had a significantly more diverse range of gut bacteria in comparison with other men in the study — and science now shows that the richer our gut flora, the healthier we are.
We all suffer emotional strain at times, so it’s important to keep stress in check. This kind of mental tension can also affect the gut, and vice versa. Stress can reduce the amount of friendly bacteria in your digestive system, as can cytokines, defensive molecules that the gut produces during infection. Pro-inflammatory cytokines can disrupt brain chemistry, making people more vulnerable to anxiety and depression.
Stress affects gut microbes even at the moment of birth. A nervous mum can pass her anxiety on to her offspring through altered gut bacteria, which her baby receives during delivery.
In 2013, US animal research revealed that babies born to stressed mothers had 20 genes adversely affected by a reduction in the ‘good’ bacterium Lactobacillus. These genes included those involved in the production of new brain cells and the growth of brain connections. Maternal stress also lowered the levels of a chemical that protects the brain from harmful oxidative stress.
During times of stress, your muscles constrict. This includes gut muscles, so ridding yourself of as much stress as possible helps your digestive system to function. Relaxing helps your body lift its levels of healthy microbes and lower its levels of stress chemicals. So why not stretch into a yoga class or some tai-chi moves? You can easily learn and practise these excellent calming techniques every day.